Lords from all main political parties will unite next week in a last-ditch
attempt to block the Government’s introduction of gay marriage.

Peers expect the Upper’s House debate over same sex weddings will go through the night or even into a second day, with a key vote that could scupper the policy regarded as “too close to call”.

The former head of the British army Lord Dannatt and Lord Lothian, a former Conservative Party chairman better known as Michael Ancram, are amongst those set to criticise the draft legislation in next Monday’s session.

Other opponents will include Lord Waddington, a former Home Secretary, Lord Luce, who served as a minister in Baroness Thatcher’s government, and Lord Singh of Wimbledon, a respected figure in the Sikh community.

The Sunday Telegraph has also established that the senior Tory Baroness Warsi, a practising Muslim, refused to lead the bill through the House of Lords when asked to do so by David Cameron, the Prime Minister.

Some peers believe dozens Lords who rarely attend Parliament will flock to Westminster to make their position on homosexual marriage clear.

Seventy-five members of the Lords have already asked to speak in the debate, suggesting that dawn could rise on the Tuesday morning before all the peers have their say.

Government whips are fighting calls to allow the Lords to hold a second day of debate on what has become the one of the most emotive issue in parliament for many years.

Some critics of same sex marriage legislation believe the policy undermines the institution of marriage while others simply regard it as a “distraction” from the country’s economic problems.

Mr Cameron has championed homosexual weddings and Tory strategists hope it will entice new voters to the party at the next general election.

However, gay marriage so far appears only to have played havoc with the Conservative party’s grassroots, sparking resignations of members and fierce criticism of the Prime Minister.

Lord Luce said: “You can’t suddenly pounce on the 2,000 year-old institution of marriage after such little consultation and with such little thought.

“This is all part of the Prime Minister’s 'modernisation’ of our party, whatever that word is supposed to mean. This is all being handled in a very slap happy, careless manner.”

This weekend there is speculation in Westminster that the Most Rev Justin Welby, the recently appointed Archbishop of Canterbury, will also voice his concerns about the policy in next week’s debate. One of his predecessors, Lord Carey of Clifton, has already put his name down to speak.

Lord Dear, the retired chief constable of West Midlands Police and crossbench peer leading opposition to the Bill, said that critics of the policy were not “anti-homosexual”.

“This is ill-thought through legislation that is being rushed through,” the peer said. “There are some 8,000 further amendments that will be necessary to existing legislation because of this single policy.

“Of those who said they would speak about half seem to be opposed. I really think the vote will be too close to call.”

If the Government loses the Bill, ministers could use the Parliament Act to drive the policy through. However, Lord Dear thinks this is unlikely.

He added: “The Parliament Act has been used only three times before. Opposition in the Commons in the Commons was strong and there is not strong appetite amongst the public for this.”

Lord Stoddart, an independent Labour peer, described the whole concept of gay marriage as “bogus”. He said he was baffled as to how gay people and lesbians would “consummate” their marriage.

“Without consummation the marriage could be annulled at any point,” the peer said. “No one has been able to explain to me how homosexuals or lesbians would be able to actually consummate their marriage.

“People who voice concerns about this policy are told that we are bigots. I honestly think the bigots are on the other side of the argument. Many homosexual people do not want this.”

Those peers who will vote with the Government include Lord Browne, the former BP chief executive and friend of Lord Mandelson, and Lord Deben, the former Conservative minister better known as John Gummer.

Lord Hodgson, a Conservative peer who expects to back the bill, said that the policy was “clearly a very divisive issue”.

He said: “I have children in their twenties who wonder what all the fuss is about and friends in their sixties who think this is the end of the world.

“The number of people who have put down to speak is quite staggering. We could go through the night on this… it looks very close.”

Nick Herbert, the Conservative MP who has campaigned for same sex marriage, said: “The Lords always has an important scrutiny role but they can’t ignore the fact that this BIll passed the elected House with a two to one cross-party majority.

“The Bill was debated for hours in Commons committee and every independent poll shows majority public support for the measure.

“Equal marriage is being introduced across the western world and I don’t believe peers will want to be out of step with changing attitudes.”